Kearns was born of Irish descent in Ontario, Canada. From Nebraska he moved to Park City, Utah in 1883, becoming wealthy as a silver prospector and developer. A delegate to the state constitutional convention in 1895, he was elected U.S. Senator in 1901 and served until 1905. He was a civic leader and newspaper publisher in Utah until his death in 1918. His widow Jennie founded St. Ann's Orphanage in Salt Lake City, and later donated the couple's home to the state; it became the governor's residence.